This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1998). All Rights Reserved.

Overview

This document describes the registration of the MIME sub-type
image/tiff. The baseline encoding is defined by [TIFF].

Internet Fax Working Group

This document is a product of the IETF Internet Fax Working Group.
All comments on this document should be forwarded to the email
distribution list at <ietf-fax@imc.org>.

1. Abstract

This document describes the registration of the MIME sub-type
image/tiff. The baseline encoding is defined by [TIFF]. This
document refines an earlier sub-type registration in RFC 1528
[TPC.INT].

2. TIFF Definition

TIFF (Tag Image File Format) Revision 6.0 is defined in detail by
Adobe in [TIFF]. The documentation can be obtained from Adobe at:

A copy of this specification can also be found in:
ftp://ftp.adobe.com/pub/adobe/devrelations/devtechnotes/pdffiles/
tiff6.pdf

While a brief scope and feature description is provided in this
section as background information, the reader is directed to the
original TIFF specification [TIFF] to obtain complete feature and
technical details.

2.1 TIFF Scope

TIFF describes image data that typically comes from scanners, frame
grabbers, and paint- and photo-retouching programs. TIFF is not a
printer language or page description language. The purpose of TIFF is
to describe and store raster image data. A primary goal of TIFF is
to provide a rich environment within which applications can exchange
image data. This richness is required to take advantage of the
varying capabilities of scanners and other imaging devices. Though
TIFF is a rich format, it can easily be used for simple scanners and
applications as well because the number of required fields is small.

The image/tiff content-type was previously defined in RFC 1528 as
containing TIFF 6.0 encoded image data, with specific reference made
to a subset known as TIFF Class F. This document re-defines the
original image/tiff definition to refer to all of the profiles and
extensions that build on TIFF 6.0 [TIFF] encoded image data,
consistent with existing practice for TIFF aware Internet
applications. This definition is further enhanced by introducing the
new "application parameter" (section 3.2) to enable identification of
a specific subset of TIFF and TIFF extensions for the encoded image
data.

3.2 Application parameter

There are cases where it may be useful to identify the application
applicable to the content of an image/tiff body. Typically, this
would be used to assist the recipient in dispatching a suitable
rendering package to handle the display or processing of the image
file. As a result, an optional "application" parameter is defined
for image/tiff to identify a particular application's subset of TIFF
and TIFF extensions for the encoded image data, if it is known. No
values are defined in this document.

Example using a fictional value 'foo':

Content-type: image/tiff; application=foo

There is no default value for application, as the absence of the
application parameter indicates that the encoded TIFF image is
Baseline TIFF or that it is not necessary to identify the
application. It is up to the recipient's implementation to
determine the application (if necessary) and render the image to the
user.

There is no format specified for the value of this parameter
in addition to that specified by [MIME1]. Various
applications of TIFF may define values as required. New
values should be defined in standards track RFCs and the
values should be registered with IANA, using the
registration form included in Appendix A. There is no
default value for application, as the absence of the
application parameter indicates that the encoded TIFF image
is Baseline TIFF or that it is not necessary to identify the
application. It is up to the implementation to determine
the application (if necessary) and render the image to the
user.

Encoding considerations: Binary or Base-64 generally preferred

Security considerations:

TIFF utilizes a structure which can store image data and
attributes of this image data. The fields defined in the
TIFF specification are of a descriptive nature and provide
information that is useful to facilitate viewing and
rendering of images by a recipient. As such, the fields
currently defined in the TIFF specification do not in
themselves create additional security risks, since the
fields are not used to induce any particular behavior by
the recipient application.

TIFF has an extensible structure, so that it is
theoretically possible that fields could be defined in the
future which could be used to induce particular actions on
the part of the recipient, thus presenting additional
security risks, but this type of capability is not
supported in the referenced TIFF specification. Indeed, the
definition of fields which would include such processing
instructions is inconsistent with the goals and spirit of
the TIFF specification.

Interoperability considerations:

The ability of implementations to handle all the defined
applications (or profiles within applications) of TIFF may
not be ubiquitous. As a result, implementations may decode
and attempt to display the encoded TIFF image data only to
determine that the image cannot be rendered. The presence
of the application parameter may aid in allowing this
determination before dispatching for rendering. However, it

Appendix A: IANA Registration form for new values of Application
Parameter

To: IANA@isi.edu Subject: Registration of new values for the
Application parameter
of image/tiff

MIME type name:

image/tiff

Optional Parameter:

Application

New Value(s):

Application=foo

Description of Use:

foo - ("foo" is a fictional new value used in this message as an
example, it is to be replaced with the new value being
registered. Include a short description of the use of the
new value here. This must include reference to a standards
track RFC for the complete description; the use of the
value must be defined completely enough for independent
implementation. )

Security Considerations:

(Any additional security considerations that may be introduced by use
of the new parameter should be defined here or in the referenced
standards track RFC.)

Person & email address to contact for further information:

(fill in contact information)

INFORMATION TO THE SUBMITTER:

The accepted registrations will be listed in the "Assigned Numbers"
series of RFCs. The information in the registration form is freely
distributable.

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